When an eye develops a cataract and the natural lens becomes clouded, the lens materials, i.e., lens cortex and lens nucleus, are removed through an opening made in the anterior capsule. It is called extracapsular cataract extraction. In most of the cases, intraocular lenses are implanted in the residual lens capsule called the lens capsular bag. It is difficult to remove lens epithelial cells during cataract surgery. Postoperatively lens epithelial cells proliferate and migrate toward the center part of the residual posterior capsule to cause visual disturbance. This process is called posterior capsular opacification or secondary cataract. The clouded posterior capsule with proliferated lens epithelial cells can be disrupted by YAG laser and the visual axis can be cleared to restore the vision. This treatment is called YAG laser capsulotomy. However, the YAG laser treatment exposes patients to the risk of severe visual impairment or loss of vision by developing retinal detachment, cystoid macula edema and glaucoma. The development of retinal detachment and cystoid macular edema following the YAG laser treatment is thought to be related to the disruption of the anatomical barrier of the posterior capsule and the loss of the stability of the vitreous. In addition, the instrument required for YAG laser capsulotomy is expensive as is the cost for the treatment. Accordingly, there is a great need for a method to reduce the complications related to cataract surgery.
There have been many attempts to eliminate posterior capsular opacification. One promising attempt is to remove central areas of the anterior and the posterior lens capsules in a circular fashion, and fix an intraocular lens by the anterior and the posterior lens capsules (U.S. Pat. No. 6,027,531 to Tassignon.). However, there are some drawbacks of the intraocular lens and the use thereof. One of the drawbacks of the intraocular lens is a lack of stability, especially in early postoperative days. This is because, during the one week following cataract surgery, the posterior capsule is not taut. There is a risk of luxation of the intraocular lens into the anterior chamber or into the vitreous. In addition, the visual acuity will not be stable while the lens capsule is not taut in the early postoperative days. Furthermore, it is technically difficult to adjust and fix the intraocular lens to the openings of both the anterior and the posterior lens capsules.
From a different point of view, an intraocular lens for fixation by a lens capsular opening was disclosed by U.S. Pat. No. 5,697,973. The disclosed intraocular lens is intended for use when the capsular bag is destroyed during removal of a cataract. The intraocular lens comprises a lens and an annular ring having upper flange and lower flange and an inner wall interconnecting said flanges. Alternatively, an intraocular lens disclosed in U.S. Pat. No. 5,697,973 has a plurality of concentric circular grooves. The structures of the disclosed intraocular lenses are very complicated for manufacturing.